How did the Indigenous population of California change from before European contact to the late 19th century?

Before European contact, the Indigenous population of California was estimated at approximately 275,000 people. Following the arrival of Spanish colonizers in 1769, Native communities experienced a period of profound cultural rupture, characterized by forced relocation to missions, compulsory labor, and conversion to Christianity.1

The population suffered a catastrophic decline due to the introduction of European diseases to which they had no immunity, as well as displacement and violence associated with colonial expansion. This decline accelerated significantly with the gold rush that began in 1848, which brought hundreds of thousands of Euro-Americans to the region. By the closing decades of the 19th century, the Indigenous population had collapsed to approximately 15,000 individuals. This devastating demographic loss, which saw roughly 80 percent of the Native population die during the gold rush era alone, has been described by some as genocidal.213